Eclipse: The resource is not on the build path of a Java project

Question

I have been given a Source Folder (src) of a Java Project. I have created a .project file, kept it inside that folder and imported that Project int

Answer 1

Using Eclipse Oxygen with a multimodule maven project make sure you're not editing the file in the maven parent project.

This caused the "Open Declaration', 'Open Type Hierarchy' and 'Open Call Hierarchy' to show the dreaded dialog in question. It would even mess with the autocomplete.

Make sure you are not editing the parent project and instead edit the child project to avoid the error.